Fluoroscopically-guided procedures have become a tool in the diagnosis and treatment of coronary artery disease. However, increasing concern is expressed at the high level of x-ray exposure which can be delivered. A low-dose scanning-beam digital x-ray (SBDX) system has been developed to address this problem. The SBDX system uses electronic scanning and a detector array to provide high resolution images at 30 frames/sec. System geometry results in a negligible level of detected scattered radiation. Preliminary results indicate a several fold reduction in patient exposure, with larger patients enjoying the greatest decrease. The goal of this proposal is to validate the SBDX system for the application of diagnostic and interventional cardiac angiography. Five specific aims are proposed: 1) Compare the basic imaging properties (modulation transfer function, detective quantum efficiency, noise power spectrum) of SBDX and a conventional angiographic/interventional image-intensifier-based system; 2) Measure the x-ray exposure reduction provided by SBDX using phantom and porcine models; 3) Validate that the clinically important tasks of coronary angiography and ventriculography can be performed accurately using the SBDX system. This will be performed in a porcine model; 4) Investigate the potential improvements in videodensitometric quantitation algorithms provided by the scatter-free nature of the SBDX images. This will be performed in phantom and porcine models; and 5) Demonstrate in patients that accurate coronary angiographic results can be obtained using SBDX. The successful completion of this research will provide a coronary angiographic/interventional x-ray system with previously unachieved levels of safety without compromising image quality.